Just what are rtx costs?

[Joern Rennecke]

Quoting Richard Guenther <richard.guenther@gmail.com>:

>> So are you saying that we should remove the recursive nature of the
>> rtx_cost/targetm.rtx_costs interface, and have the backend handle any
>> recursion itself?  I.e. targetm.rtx_costs only ever sees a complete
>> (but perhaps invalid) instruction pattern?  Or would you still keep
>> the current recursion?
>
> I would say yes to that - kill the recursion.

But the recursion is already optional.  If you don't want to use recursion
for your port, just make the rtx_costs hook return true.
There is no need to break ports that are OK to use the recursion in rtlanal.c
partially or in whole.